Some kiwi varieties may be less allergy-inducing

NEW YORK (Reuters Health) - With kiwifruit becoming ubiquitous in grocery stores worldwide, reports of allergic reactions to the fruit have also increased. But some varieties may be less likely than others to trigger allergies, a small study suggests.

In tests of 37 adults with kiwi allergies, researchers found that certain cultivars of the fruit -- including the "gold" variety -- tended to be less allergenic than the common deep-green variety known as Hayward.

The findings, reported in the Journal of Allergy and Clinical Immunology, raise the possibility that people who avoid kiwi because of allergies might be able to reintroduce the fruit into their diets. Larger studies are needed, however, before they can be given the green light.

The kiwifruit, native to southern China, was once considered an "exotic" fruit, but since the 1970s its availability and popularity has increased worldwide. With that wider consumption has come an increase in incidents of allergic reactions to kiwi.

Symptoms of kiwi allergy can include tingling, itchiness and inflammation in the mouth and throat, skin rash, stomach pain and vomiting, and even severe reactions like breathing problems or a sudden drop in blood pressure.

Recent studies from Sweden, Finland and France indicate that kiwi has become one of the top-10 sources of food allergies in those countries, noted Dr. Karin Hoffmann-Sommergruber, an associate professor at the Medical University of Vienna, in Austria.

For the current study, Hoffmann-Sommergruber and her colleagues looked at whether different kinds of kiwi vary in their tendency to provoke immune system reactions and symptoms in people with allergies to the fruit.

They assessed six kiwi varieties, including Hayward, the most commonly available cultivar, with the familiar medium-brown skin and bright-green flesh; and Summer 3373, a variety in the same kiwi "species" as Hayward but with light-green flesh. The latter came to the market more recently but its availability is growing.

The other tested kiwifruits included Hort 16A, marketed as "Zespri Gold" and the most widely available golden-fleshed variety; Jintao, a golden variety newer to the market; and two varieties of a kiwi species called Eriantha expected to come to market in the next 10 to 20 years; they are smaller and lighter-skinned than other kiwi varieties and have deep-green flesh.

All of the study participants underwent skin testing, in which a thin needle was first injected in the fruit and then into the participant's skin to gauge the immune system reaction. In general, the researchers found, the Hayward kiwi triggered the most significant skin reactions, while the lighter-green Summer and gold Hort 16A varieties garnered the mildest reactions.

A subgroup of participants also underwent food-challenge tests, in which they were gradually given small amounts of the Hayward, Summer and Hort varieties under medical supervision.

Again, the Hayward kiwi appeared the most allergenic. Two of 11 study participants had severe reactions -- including breathing problems or cardiovascular symptoms -- to the variety. Of the rest, most had moderate symptoms, like abdominal pain and diarrhea, and two had no symptoms.

Two of three food-challenge participants given the Summer variety had mild oral reactions and one had oral symptoms and a skin rash. Of eight participants given the gold Hort variety, two had no symptoms, and the rest had mild or moderate ones.

Neither the Summer nor the Hort varieties triggered a severe reaction in any subjects.

Previous research had indicated that the allergenicity of the major kiwi species varies, Hoffmann-Sommergruber told Reuters Health in an e-mail.

In general, the major allergy-triggering protein in kiwi exists in a 50-times higher concentration in green kiwifruit compared with golden kiwi, she added.

The current findings, according to Hoffmann-Sommergruber and her colleagues, may help sort out which specific kiwi varieties can be safely tolerated by the allergy-prone. But, they say, further research in large groups of patients is still necessary.

The worldwide prevalence of kiwi allergy is not clear. In the U.S., it's estimated that three percent to four percent of adults and about six percent of young children have an allergy to some type of food -- with milk, eggs, nuts, fish, soy and wheat accounting for the bulk of those reactions.

People with allergies to pollen are more likely than others to react to kiwi (as is true of a number of other fruits). People with latex allergies also show an increased risk of kiwi allergy due to similarities in the allergy-triggering proteins found in latex and kiwi.